[apersson850]

The Polestar optimizations, at least those available here in Sweden, don't change any emission values. Well, of course they do, when you use the new power, but not as long as you drive as they do when testing the car. Hence no impact to taxes or anything else.
Also, in this country, insurance isn't affected. It's considered to be the same thing as any other accessory.

You're obliged to register it with the authorities, though. But if you "forget", nothing happens. They don't see it at the annual inspection.

I'd say that the Polestar modification to my car, an XC70 D5, makes a difference. Not that it's much if you look at the peak figures, from 215 hp/440 Nm to 230 hp/470 Nm, but if you look at the power/torque plot, you can see that over quite a broad range of revs, then engine is quite a bit more powerful. It've very good for towing heavy and large trailers.